Pivot Tables

For some reporting started working on some pivot tables. To me these tables are one of those initial rich data visualization formats.
What is it ? :
"In SQL, a pivot table is a set of data that is transformed from a collection of separate rows to a collection of columns. In relational databases, such as Microsoft SQL Server, Oracle and MySQL, pivot tables can be used to simplify extensive data in order to make it easier to read and understand. To create a pivot table, an aggregate is used against a set of data to distribute multiple rows of a single column into a single row with multiple columns. This essentially pivots the result set sideways."

How to :

-Pivot by Aggregated Case Statement

By using an aggregate function (SUM, AVG, MIN, MAX) around a case statement in a SQL query, we are able to achieve the same result as the PIVOT function with less work.

- Sample data: To better understand a pivot table, an example of some sales data is listed here. Copy the following into Microsoft SQL Server Management Studio to try out the examples.

Create table PivotTestTable
(CustName varchar(8),
Item_Type varchar(8),
Item_Amount numeric(6,2))

insert into #PivotTestTable
select 'Jason', 'Computer', 435.34
union
select 'Jason', 'Software', 243.54
union
select 'Jason', 'Monitor', 158.23
union
select 'Alison', 'Computer', 345.89
union
select 'Alison', 'Software', 78.78
union
select 'Alison', 'Monitor', 123.45

- UnPivoted data : When the temp table, #PivotTestTable, is queried, the result is the following.

CustName Item_Type Item_Amount
-------- --------- -----------
Alison Computer 345.89Alison Monitor 123.45
Alison Software 78.78Jason Computer 435.34
Jason Monitor 158.23Jason Software 243.54

As you can see, the result set shows two customers, Alison and Jason, who have purchased three different types of items. There are six rows of data for two customers. If we wanted to see the data in a single row per customer, we would use a pivot table to achieve the desired result.

- Pivoted data : Try the following query and see how the output looks now:

SELECT
CustName as Total_Sales_By_Cust,
sum(case Item_Type when 'Computer' then Item_Amount end) as Computer,
sum(case Item_Type when 'Monitor' then Item_Amount end) as Monitor,
sum(case Item_Type when 'Software' then Item_Amount end) as Software
FROM PivotTestTable
GROUP BY CustName

Or the same can be done as :

SELECT
CustName as Total_Sales_By_Cust,
sum(Item_Type = 'Computer') as Computer,
sum(Item_Type = 'Monitor' ) as Monitor,
sum(Item_Type ='Software' ) as Software
FROM PivotTestTable
GROUP BY CustName

Or you can even COUNT instead of SUM

Currently I am only playing with the SQL to generate the pivot tables; But yeah, there are couple of JS library that you can utilize to play with the Pivot tables on the fly on the client :) :

1. Pivot.js
2. jQuery.pivot

Reference:

• http://www.ehow.com/about_5336679_pivot-table-sql.html
• http://dev.mysql.com/tech-resources/articles/wizard/print_version.html
• http://forums.mysql.com/read.php?52,527105,527163

jQuery Datatables plugin and Codeigniter

Just got an work around for the jQuery datatables wrapper [IgnitedDatatables] and made it working on a project to load huge data. As I din get any neat info I had to dig little deep both into datatables plugin and the wrapper and finally made a work around for me. Here in this post I am basically sharing my experience along with keeping records of what and how I did :)
The js I am using on the view to create the datatable and load using ajax is as follow [don try to run on jsFiddle 'cz it has lots of garbage- will clean it up :| ] :


Code on the controller:


And finally the model:


I will write in details on it - how I actually worked on later on this post.
Tips:

1. For the callback function for the wrapper to work you need to create a helper file where you need to put all the callback functions.
2. As the wrapper somewhat works as the model should work I have called and made use of it in my model class.

Reference:

1. jQuery Datatables plugin api
2. Server side data processing using Datatables plugin
3. IgnitedDatatables function reference; and Method Chaining example
4. Example usage code for the IgnitedDatatables library [independent of Codeigniter]
5. Sample MySql Database [Sakila :)]

Manipulating Auto Increment values in MySql

1. Set the MySql variables auto_increment_increment and auto_increment_offset variables.
2. Play with the Auto_Increment in Information schema.

To start with an AUTO_INCREMENT value other than 1, you can set that value with CREATE TABLE or ALTER TABLE, like this:

ALTER TABLE tbl AUTO_INCREMENT = 100;

Note:It is not possible to confine the effects of these two variables to a single table, and thus they do not take the place of the sequences offered by some other database management systems; these variables control the behavior of all AUTO_INCREMENT columns in all tables on the MySQL server. If the global value of either variable is set, its effects persist until the global value is changed or overridden by setting the session value, or until mysqld is restarted. If the local value is set, the new value affects AUTO_INCREMENT columns for all tables into which new rows are inserted by the current user for the duration of the session, unless the values are changed during that session.